1. Field of the Invention
The present invention relates to mounting structures for PCV valves (positive crankcase ventilation valves) used for controlling flow of blow-by gas.
2. Description of the Related Art
A known PCV valve mounting structure is disclosed, for example, in Japanese Laid-Open Publication No. 6-229221. The mounting structure disclosed in this publication is shown in a vertical sectional view in FIG. 6.
As shown in FIG. 6, according to the known mounting structure, a base end portion (lower end portion as viewed in FIG. 6) of a PCV valve 130 is mounted to a cylinder head cover 110, and a base end portion (upper end portion as viewed in FIG. 6) of the PCV valve 130 is mounted to a surge tank 112. More specifically, a flat valve mounting portion 120 is formed on the upper portion of the cylinder head cover 110, and a valve mounting hole 136 is formed in the valve mounting portion 120. The base end portion of the PCV valve 130 is inserted into the valve mounting hole 136, so that a gas inlet port 142 formed at the base end portion of the PCV valve 130 communicates with inside of the cylinder head cover 110. A flat valve mounting portion 122 is formed on the lower portion of the surge tank 112, and a valve mounting hole 144 is formed in the valve mounting portion 122. A terminal end portion of the PCV valve 130 is inserted into the valve mounting hole 144. Therefore, a gas reflux port 150 formed at the terminal end portion of the PCV valve 130 communicates with inside of the surge tank 112. When a load is applied to an engine, a negative pressure is produced by an intake air and can operate the PCV valve 130 mounted to the cylinder head cover 110 and the surge tank 112 as described above for adjusting the amount of the brow-by gas refluxed from within the cylinder head 110 to the surge tank 112 when the brow-by gas produced at the engine is refluxed into an intake air system of the engine.
In the case of the known mounting structure, the base end portion of the PCV valve 130 is inserted into the valve mounting hole 136 while the terminal end portion of the PCV valve 130 is inserted into the valve mounting hole 144 formed in the valve mounting portion 122 of the surge tank 112. However, an intermediate portion of the PCV valve 130 positioned between the base end portion and the terminal end portion is exposed to the outside at a position between the cylinder head cover 110 and the surge tank 112. Therefore, if the intermediate portion of the PCV valve 130 is exposed to the atmospheric air (in particular, air stream produced during running of a vehicle) when the atmospheric air is at an extremely low temperature, a water content contained in the blow-by gas flowing through the PCV valve 130 from the gas inlet port 142 to the gas reflux port 150 may be frozen.
Therefore, there is a need in the art for a PCV valve mounting structure that can inhibit or prevent, a water content contained in the blow-by gas from being frozen up within the PCV valve.